I have a tough question. I just got an Nike + iPod Sports Kit. I want to calibrate it using what I assume is an accurate distance - the local high school 400m track. The question is, where is the 400m measured from? Is it Lane 1? Where in Lane 1? At the painted line on the inside of the lane? The outside of the lane? In the middle of the lane?

Inside line of lane one from the finish/start line, then the inside of every other lane if you start from the stagger line in each lane for a 2-turn stagger.
I guarantee your equipment is not sensitive enough to register the difference between the inside and the middle of the lane.

Yes, that too
Nice book cover in your avatar by the way. Still waiting for the sequel...

Yeah, aren't we all! Probably not happening though...sigh...

"It is simply that we can all be good boys and wear our letter sweaters around and get our little degrees and find some nice girl to settle, you know, down with...Or we can blaze! Become legends in our own time, strike fear in the heart of mediocre talent everywhere! We can scald dogs, put records out of reach! Make the stands gasp as we blow into an unearthly kick from three hundred yards out! We can become God's own messengers delivering the dreaded scrolls! We can race dark Satan himself till he wheezes fiery cinders down the back straightaway....They'll speak our names in hushed tones, 'those guys are animals' they'll say! We can lay it on the line, bust a gut, show them a clean pair of heels. We can sprint the turn on a spring breeze and feel the winter leave our feet! We can, by God, let our demons loose and just wail on!"
-Quenton Cassidy

Nice. I like that passage. Never read the book but I've seen that quote before and I like it. Especially the clean heels part.
Isn't there another guy using the Once A Runner cover as his avatar too? Or am I imagining things?

And too there were questions: What did he eat? Did he believe in isometrics? Isotonics? Ice and heat? How about aerobics, est, ESP, STP? What did he have to say about yoga, yogurt, Yogi Berra? What was his pulse rate, his blood pressure, his time for 100-yard dash? What was the secret, they wanted to know; in a thousand different ways they wanted to know The Secret. And not one of them was prepared, truly prepared to believe that it had not so much to do with chemicals and zippy mental tricks as with that most unprofound and sometimes heart-rending process of removing, molecule by molecule, the very tough rubber that comprised the bottoms of his training shoes. The Trial of Miles, Miles of Trials. How could they be expected to understand that?

Huh? I though this thread was about swallows….
I think Xanadu came the closest. I thinks it’s actually 20 cm from the inside line of Lane 1. I found the following:
“One simple method for measuring a track is to rent a surveyor's wheel from a local equipment rental agency for a few hours (or borrow one if possible) and actually measure the length of Lane 1. …After resetting the measurement counter to zero, roll the wheel along a path 20cm or 8" out from the inside line of Lane 1 (30cm or 12" out from a curb) for about three laps and divide the total reading by the number of laps measured.”
- from http://www.philsport.com/narf/atrack.htm
“Rules specify that a lane's length is not measured around the outer edge of the lane's inner boundary but around an undrawn curve, called the measure line, which is 20 centimeters outside that outer edge.”
- from http://www.sciencenews.org/articles/20030809/mathtrek.asp
Regarding being able to register the difference between inside vs. the middle. I think Xanadu is right. I found this:
“The standard lane width for most high school and college outdoor tracks in the United States is 42 inches. This gives 6.70 meters of extra distance per lane per lap.”
- from http://www.sciencenews.org/articles/20030809/mathtrek.asp
Therefore, a half of a lane would yield a 3.35 m difference per lap or 3.35/400 --> 0.8375%. I doubt the iPod can measure to this accuracy, especially since they only advertise 90% accuracy (uncalibrated). Well, I will take my own measurements and see how it does.

Isn't there another guy using the Once A Runner cover as his avatar too? Or am I imagining things?

What? And here I was sitting all pleased of myself and my choice of avatar.....
I'll challenge him to a "Once A Runner" quote-off for rightful owner of the avatar!
(I can recite the entirety of that quote by heart, it makes for an impressive performance)
My friends always said I looked like the guy on the cover.

I doubt the iPod can measure to this accuracy, especially since they only advertise 90% accuracy (uncalibrated). Well, I will take my own measurements and see how it does.

Yeah, XanaduStone had it right. It's the inside of Lane 1 on a 400m track.
Regarding the iPod. I run with a woman who just got one of these gadgets for Christmas. She diligently followed the instructions and calibrated it on a 400m oval at a local high school. In that last couple weeks when we have done our easy 5-milers at lunchtime from our office, her iPod thingy has reported our runs to be anywhere from 4.9 to 5.1 miles. And yet we are always running the same exact 5.0 mile out and back route. If we're running about 8:00 pace it is pretty close. If we're running faster it is long and if we're running slower it is short. So an "accelerometer" may be more accurate than a pedometer, but not by much.

Runners run.

va

posted: 1/12/2007 at 8:57 AM

Thanks for the data.
+/- 0.1 mile in a 5 mile run is a +/- 2% error. I guess I would be happy if I got that kind of accuracy.
Is there anyone elso with a calibrated iPod that has any test data to share?
What about accuracy test results for other GPS and pedometer devices?

+/- 0.1 mile in a 5 mile run is a +/- 2% error. I guess I would be happy if I got that kind of accuracy.

Agreed. We had that very conversation yesterday as we were coming in from our run. +/- 2% is good enough for general runs. Of course the thing would likely be further off if you did workouts with it because the variation in pace would be that much greater and you want to be most accurate for workouts, but I think for general runs it is decent.

Runners run.

va

posted: 1/12/2007 at 9:27 AM

I hear you. I guess it would be best to calibrate the iPod at your long term average pace (i.e., a pace that includes multiple run types). At least, this would give you the best long term accuracy.
I guess I should run some accuracy experiments including variations of pace.